Method:
Six 100ml beakers are to be filled with a measured amount (80ml) of different concentrations of sucrose solutions measured at 0%, 20%, 40%, 60%, 80% and 100% using an100ml measuring cylinder. We are using Asda White potatoes. Cut 18 potato cylinders (3 for each beaker) using an apple corer. We use an apple corer of 1.1cm to ensure that the diameter and therefore the surface areas remain the same. The potatoes are left raw (if boiled, the cell membranes would be destroyed) and are cut to the same length and mass (using a ruler and using some electronic scales). The cylinders are wiped (to make sure that they are clean and do not have anything on them which would disrupt the experiment) and placed in solution. The temperature of the sucrose solutions is recorded. The experiment is to be carried out under lab conditions of about 25°c and the cylinders are to be left 2 days. They are left for 2 days as this seems an appropriate period of time as if left any longer, the potatoes may start to disintegrate, and if left for any sooner, then a reaction may not even take place. A result for each potato cylinder will be taken from each beaker to calculate the averages so that graphs and conclusions can be drawn.
Hypothesis:
I think that the potato cylinders with the higher concentrations of sucrose (80%, 100%) are most likely to decrease in mass and length. I think this because there is a lower water potential in the sucrose solution, meaning that the water molecules in the potato cylinder will osmose to the solution. This means that the cells will become flaccid due to the smaller amount of water in the vacuole. The potatoes in the lower concentrations of sucrose (0%, 20%) will increase in mass and length. This is due to the high water potential in the solution. The water molecules in the solution diffuse to the lower water potential in the potato, making the vacuoles full of water, leading the cell to become turgid and therefore increase in mass and length. The potato cylinders in the medium concentrations of solution (e.g. 40% and 60%) will probably stay the same as the water potential in the solution and the water potential in the potato are very similar.
Conclusion:
My graphs are reasonably conclusive. The change in length and change in mass graphs both have negative correlation that shows that if the concentration of sucrose higher, then the length and mass of the potato cylinders is lower. Osmosis proves this as the water potential in the potato is higher than the water potential in the high sucrose solution, meaning that the water molecules in the potato will osmose to those in the high sucrose solution leaving the potato cylinder smaller than its original shape as it has lost water. I accept my hypothesis as in it I thought that the potato cylinders in the higher concentrations of sucrose would become smaller and the potato cylinders in the lower concentrations of sucrose would become bigger. This was true as the results show that the potatoes in high sucrose solution decreased in mass and length and the potatoes in the low sucrose solutions increased in mass and length.
Evaluation:
Our results are quite accurate. If you were to join the points on the graph into a line then I think that you would be surprised by the randomness of it. On the change in mass graph there is one ridiculous anomaly which was obviously due to bad measuring or adding up. I don’t think that my experiment was that reliable, as our results were a little abnormal. I think that if the potato cylinders were the same mass and length at the start then the results may have been a little more accurate. You have to make sure that they are measured and weighed precisely otherwise the results can be way out. If I had done 11 overall tests at every 10% rather than 6 overall tests at every 20% then we would have a more accurate diagram to support the experiment. The experiment would also be more conclusive if I had done the entire experiment more than once. If I had done it 3 times then the averages would be more accurate. I do not think that the evidence I have is enough to support a firm conclusion.
